Starter gearing for internal combustion engines



May 16 1951 J. J. DIGBY 2,984,115

STARTER GEARTNG FOR INTERNAL coMBusTIoN ENGINES Filed oct. 12. 1959 6 i g l l?? 3 5; 171516 MS L7nlslymzz.

WITNESS: BY

M52. @mE-E.. WQ@ d ATTO NET United States Patent O STARTER GEARING FoR INTERNAL COMBUS- 1- TIoN ENGINES James J. Digby, Elmira, NX., assignor to The Bendix The `present invention relates to starter gearing for internal combustion` engines and more particularly to that type in` which the gearing is automatically meshed and d emeshctL, Vandcentrifugal latch means are incorporated for delaying the demesh until the engine is reliably self- Operative,

In gearing of -this type asemployed to start the high speed automotive engines presently in vogue, it is neces. sary to calibrate the latch means to prevent the demeshing of the drive pinion until it has been accelerated to a high speed of rotation, in order to ensure against false starts. This ,tends to make the demeshing action rather sluggishwhile the pinion, barrel, control nut and screw shaft associated therewith are rotating at high speed. Under'these circumstances it sometimes happens that a violent vibration of the parts is set up which causes unnecessary wearl of the partsaccompanied by a Very objectionable zooming noise.

It is an object of` thev present invention to provide a novel starter drive` of the above type which is eflcient and durable while being quiet in operation under all circumstances.

lt "is lanother objectvto vprovide such a device having means for expediting thedemeshing of the gear as soon as the drive pinion has attained the predetermined rotational speed.

It is another object to provide such a device incorporating means for damping the vibration of the screw shaft during the demeshing operation.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

IFig. 1 is a side elevation, partly broken away and in section, of a preferred embodiment of the invention showing the parts in normal or idle position;

Fig. 2 is a view similar to Fig. 1 showing the parts in cranking position; and

Fig. 3 is a similar view showing the parts in their positions at the initiation of the demeshing movement of the gearing.

In Fig. 1 of the drawing there is illustrated a power shaft 1 which may be the extended armature shaft of a starting motor (not illustrated).

A sleeve 2 is rigidly mounted on the power shaft 1 as by means of a cross-pin 3, and a driving overrunning clutch member 4 is splined on the sleeve 2 as indicated at 5.

A hollow screw shaft 6 is slidably journalled on the sleeve 2 and is provided with clutch teeth 7 adapted to mate with clutch teeth 8 on thel driving overrunning clutch member 4.

A pinion 9 is slidably journalled on a reduced portion 11 of the power shaft 1 for movement into and out of mesh with a gear 12 of the engine to be started. Means for traversing the pinion into and out of mesh and for rotating the pinion to crank the engine is provided comprising a control nut 13 threaded on the screw shaft 6 and connected for rotation with the pinion 9 by means of a barrel member 14 rigidly attached to the pinion. In order to facilitate the meshing of the pinion with the engine gear, the control nut 13 is preferably splined in the barrel member 14 as illustrated, and normally pressed against a lock ring 10 by a mesh enforcing spring 20.

The travel of the control nut 13 in the meshing direction is limited by an abutment ring 15 rigidly mounted on the end of the sleeve 2 as by means of a press t on'the knurled end of the sleeve and a lock ring 16 seated in a groove in said sleeve. A thrust washer 17 is interposed between the abutment ring 15 and the adjacent end of the screw shaft 6.

Yielding means normally maintaining the teeth 8 of the driving clutch member 4 in mesh with the teeth 7 of the screw shaft 6 is provided comprising a clutch spring 18 bearing at one end against said clutch member and at its other end against an annular thrust plate 19 seated aaginst a shoulder 21 on the sleeve 2. Further yielding means for resisting axial movement of the clutch member 4 responsive to the screw-jack action of the screw shaft and control nut is provided comprising a cylindrical block 22 ofl elastically deformable material such as rubber which is located between the thrust plate 19 and a second annular thrust plate 23. Said thrust plate is slidably seated on the clutch member 4 and adapted to engage a flange 24 on said clutch member after initial compression of the clutch spring 18. A sleeve member 25 is provided with terminal flanges 26, 27 enclosing and conning the elastic member 22 and thrust plates 19 and 23 so as to normally provide a space 28 between the thrust plate 23 and flange 24 suliicient to allow the clutch teeth 7, 8 to overrun without compressing the elastic member.

The controlnut 13 has a cylindrical latch member 29 mounted for radial movement therein into and out of engagement with the screw shaft 6, a spring 31 normally holding the latch in engagement with the screw shaft. A notch 32 is formed on the periphery of the screw shaft in position to receive the latch 29 as the pinion and its associated parts approach the meshed position, whereby the latch prevents demeshing of the pinion until the rotation of the parts exceeds a predetermined speed. When the predetermined speed is exceeded centrifugal force will cause the latch 29 to be thrown radially outward with a force sufficient to overcome the retaining force exerted by the spring 31. The movement of the latch 29 releases the latch-notch engagement thereby allowing the pinion to become demeshed.

' Means are provided for expediting the demeshing movement of these parts upon release of the latch 29 in order to prevent the objectionable vibration to which reference has been made. For this purpose one or more centrifugal members here shown in the form of balls 33 are mounted in radially and axially inclined channels or passages 34 formed inthe abutment ring 15. As illustrated, these balls bear against the thrust washer 17 and as they move outward responsive to centrifugal force they will press said thrust washer and consequently the screw shaft 6 away from the abutment ring 15 as illustrated in Fig. 3, thereby exerting pressure against the driving clutch member 4, which pressure is resisted by the clutch spring 18.

In operation, starting with the parts in the positions illustrated in Fig. 1, rotation of the power shaft 1 in the direction of the arrow (a) causes the clutch member 4 and screw shaft 6 to rotate and thereby traverse the control nut 13 until it engages the thrust washer 17 which thus denes the meshing position of the pinion 9 as shown in Fig. 2. The screw-jack action of the screw shaft and control nut then thrusts the clutch member 4 backward, initially compressing the clutch spring 18 Patented May 16, 1961 3 to take up the space 28 between the thrust plate 23 and flange 24, and then compressing the elastic block 22 to provide the yielding driving connection for the cranking operation.

During the cranking operation, premature demeshing of the pinion responsive to sporadic explosions of the engine is prevented by engagement of the latch 29 in the notch 32 of the screw shaft. However, the screw shaft 6 is permitted to overrun the driving clutch member 4 by compression of the clutch spring 18 suciently to permit the teeth 7 of the screw shaft to disengage the teeth 8 of the clutch member. The speed of rotation of the power shaft under these circumstances is insutlcient to cause outward movement of the centrifugal balls 33.

When the engine becomes reliably self-operative and thereby rotates the pinion 9 and control nut 13 above the critical predetermined speed, the latch 29 moves out of the notch 32 by the operation of centrifugal force so as to permit the control nut to thread itself back on the screw shaft 6 toward idle position. The simultaneous relief of the cranking load on the starting motor permits the power shaft, sleeve 2, and the abutment ring to accelerate sufliciently to cause the centrifugal balls 33 to move outward and press the screw shaft 6 against the clutch member 4 as shown in Fig. 3. The consequent retardation of the screw shaft in relation to the rapidly `rotating control nut 13 causes the control nut and pinion to be rapidly traversed back to idle position. 'I'his pressure against the clutch spring 18 is also elective to damp any incipient vibration of the screw shaft, and/or the cooperating parts, of the character above set forth.

Although but one form of the invention has been shown and described in detail, it will be understood that changes may be made in the form and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an engine starter drive a power shaft, a driving overrunning clutch member slidably but non-rotatably mounted thereon, a hollow screw shaft slidably and rotatably mounted on the power shaft having driven overrunning clutch means normally in operative engagement with said driving overrunning clutch member, a pinion slidably journalled on the power shaft, a control nut threaded on the screw shaft, means connecting the control nut and pinion for traversing the pinion into and out of mesh with a gear of the engine to be started and for rotating the pinion to crank the engine, yielding means resisting axial movement of the driving clutch member away from its engagement with the screw shaft, and means including centrifugal elements urging the screw shaft into engagement with the driving clutch member.

2. An engine starter drive as set forth in claim 1 in which said centrifugal elements are mounted on and connected to rotate with the power shaft.

3. An engine starter drive as set forth in claim 1 ncluding `further an abutment member xedly mounted on the power shaft for limiting the movement of the control nut towards the pinion meshed position, said last mentioned means including a member mounted to rotate with said abutment member and to move radially and axially responsive to centrifugal force, and means for transmitting said axial movement to the screw shaft to urge it into engagement with the driving clutch member.

4. An engine starter drive as set forth in claim 1 including further centrifugal latch means comprising a radially movable latch rotatable with said control nut preventing demeshing movement of the control nut on the screw shaft until the control nut is rotating above a predetermined speed, said yielding means being arranged to permit the screw shaft to overrun the driving clutch member while said centrifugal latch means is effective to prevent demeshing of the pinion.

References Cited in the tile of this patent UNITED STATES PATENTS 2,549,948 Millar Mar. 27, 1951 2,791,309 Couse May 7, 1957 2,815,669 Mendenhall Dec. 10. 1957 

